PWHT Question B31.3

[jayinwww]

Table 311.1.3 states P1 material a preheat of 200°F for thickness of >1". The table name is Exemptions to Mandatory Postweld Heat Treatment.

Does that mean I must:

1. Preheat to 200°F if my material is over 1"?
or
2. Preheat to 10°C for example then PWHT if my material is over 1"?

Or is it only PWHT over 1" if required as per job and then I have an option to PWHT or Preheat to 200°F

Seems somewhat missleading.

 

[mk3223]

1. Yes
2. Yes
3. The B31.3 Code requires the P1 material to be PWHT if WT > 1” thick, and new version of Code provide the exemption if a higher preheat is used for the welding.

 

[WE91]

Also refer to Table 330.1.1, preheat vs thickness is also determined by C %. so if your over 1" thick with a C% less than .3 and plan to PWHT then your min preheat can be as low as 50F. If you are over 1" thick and are looking to exempt from PWHT you must have a 200F regardless of C% and a WPS qualified without PWHT.